Pat the fish dry with kitchen paper and evenly rub with salt, rubbing it inside the cavity as well if you are using a whole fish. Put the fish on a heatproof plate and scatter the ginger over the top.

Set up a steamer or put a rack into a wok or deep pan. Fill it with 5cm/2in of water and bring to the boil over a high heat.

Put the plate of fish on the rack, cover tightly and steam the fish until it is just cooked. Flat fish fillets will take about 5 minutes; whole fish, or fillets such as sea bass, will take 12-14 minutes. The fish should turn opaque and flake slightly but still remain moist.

Remove the plate of cooked fish and pour off any liquid that may have accumulated. Scatter the spring onions on the fish, then drizzle over the light and dark soy sauces.

Heat the two oils together in a small saucepan until smoking, then immediately pour them over the fish. Garnish with coriander and serve at once with boiled rice.

FODMAPs are short chain carbohydrates (oligosaccharides), disaccharides, monosaccharides and related alcohols that are poorly absorbed in the small intestine. These include short chain (oligo-) saccharide polymers of fructose (fructans) and galactose (galactans), disaccharides (lactose), monosaccharides (fructose), and sugar alcohols (polyols) such as sorbitol, mannitol, xylitol and maltitol.

The term FODMAP is an acronym, deriving from "Fermentable, Oligo-, Di-, Mono-saccharides And Polyols". The restriction of these FODMAPs from the diet has been found to have a beneficial effect for sufferers of irritable bowel syndrome and other functional gastrointestinal disorders (FGID). The low FODMAP diet was developed at Monash University in Melbourne by Peter Gibson and Susan Shepherd.